Incrementally extensible cathode glow indicator tube



ATT

F. B. MAYNARD Filed 00T., 10, 1956 'Ql'ma'wmwmm` Nov. 19, 1957INCREMENTALLY EXTENSIBLE CATHODE GLow INDICATOR TUBE INVENTOR Fem MAWARD BY j C/ RNE United atent @thee INCREMENTALLY EXTENSIBLE CATHODEGLOW INDICATOR TUBE Fred Maynard, Phoenix, Ariz., assignor to NationalUnion Electric Corporation, Orange, N. ll., a corporation of DelawareApplication October 10, 1956, Serial No. 615,054 12 Claims. (Cl.315-845) This invention relates to indicator tubes, and more especiallyit relates to tubes of the gaseous content cathode glow discharge kind.

A principal object o-f the invention is to provide an improved cathodeglow indicator tube wherein the glowing area can be extended andcontracted in precise incremental or decremental steps in proportion tothe successive levels of an input control voltage.

Another object is to provide an improved cathode glow discharge tubewherein the glow can be accurately extended along the length of acathode in.welldened incremental areas.

Herctofore it has been proposed to manufacture socalled extended areaglow discharge tubes wherein a cathode is arranged to have a glowproduced thereon of variable area. While there has been a considerablecommercial demand for that general kind of tube, such demand has notbeen met for a variety of reasons. Amongst these reasons are, irst, thediculty of accurately incrementing and decrementing the glow area inresponse to incremental and decremental applied voltages; second, thediiiiculty of producing such tubes in mass production with uniformity ofincremental glow area characteristics as between various tubes.

Accordingly, one of the features of this invention is the novelconstruction and design of an extended cathode glow area tube whereinuniformity and precisional accuracy of incremental glow areas can beobtained during the mass production of such tubes.

Other features and advantages not particularly enumerated will becomeapparent after a consideration of the following7 detailed descriptions,the appended claims and the attached drawing.

In the drawing, which shows by way of example certain preferredembodiments,

Fig. l is a plan View of an indicator tube according to the invention;

Fig. 2 is a sectional view of Fig. l taken along the line 2 2 thereof;

Fig. 3 is a sectional view of Fig. 2 taken along the line 3-3 thereof;

Fig. 4 is a schematic diagram showing one manner of using the tube ofFigs. l to 3 as a numerical indicator;

Fig. 5 is a magnied cross-sectional view of part of the tube of Fig. land used in explaining its operation;

Fig. 6 is a modication of the tube of Figs. l to 3;

Fig. 7 is a schematic diagram showing the device used as a voltmeter.

The tube according to this invention provides a gaseous discharge devicewhich has the function of exhibiting a visual bar, line or similarprecisely defined area of light whose length is a specific function ofor proportional to the instantaneous values of an input signal voltage.Specically the bar or line of light is in the form of a cathodic glow,the length of which may start from zero or some minimum magnitudecorresponding to the minimum of the input signal, and rising to someother maximum value corresponding to the maximum value of the inputsignal,

the intervening variable lengths of the bar or line of light thencorresponding to the intervening values of applied signal input.Furthermore, the device according to the present invention instead ofexpanding progressively smoothly with increasing values of the inputsignal, is expanded or contracted in length in discrete steps. Thenumber of these steps for any given range of input signal values or forany given physical length of the indication desired may be made anyconvenient value. As a result the device is capable of acting as adigitalizing device, in that the value of the input signal or functioncan be expressed as a discrete number of equal steps, if desired.

Referring to Figs. 1 to 3 of the drawing, the device comprises anenclosing glass envelope or bulb 10 within which is enclosed the novelelectrode mount 11 according to the invention. This mount consists of aat strip 12 of mica or similar insulating material which can beinterlocked at its opposite ends with two end mica plates 13, 14.Attached to the upper face of strip 12 is a metallic strip 15 which maybe made of any suitable metal, such for example as aluminum foil. Thismetallic layer 15 may be attached to the mica strip 12 in any convenientmanner so that it lies flat thereagainst. lf desired, the metallic strip15 may be in the form of a metallic coating applied in any well knownmanner to the surface of mica 12. The metallic strip 15 constitutes thecathode of the device on which incremental step by step glow dischargeis produced. Merely by way of example, the strip 15 may have a width ofapproximately two to three millimeters and a thickness of the order of0.001 inch.

Also extending between and suitably interlocked with the end micas 13and 14 are two lateral mica strips 16, 17. Each of these strips 16, 17has sets of aligned openings through Which pass a series of insulatingbarriers 18 which may be of ceramic, glass or other similar refractoryinsulating material. Preferably, although not necessarily, the ceramicrods 18 are of round cross-section, for example of 0.050 inch indiameter. In accordance with the invention, the barrier rods 18 aremounted in micas 16, 17 so that each of the said barrier rods engagesthe surface of the cathode strip 15. Preferably the rods 18 are spacedapart equally along the length of the cathode 15, this spacing dependingupon the size of the cathode stepped areas to be illuminated. Preferablyalso, although not necessarily, the barriers 18 are mounted at rightangles to the length of strip 15 so that the area defined between eachadjacent pair of barriers 18 and the intervening edges of the cathodestrip 15 are square or rectangular in shape.

Extending centrally along the cathode strip 15 and engaging the upperperiphery of all the barrier members 18, is a thin wire 19 which at itsopposite ends is interlocked in any suitable manner with the end micas13, 14. It will thus be seen that the anode wire 19 extends along thefull length of the cathode strip 15. The wire 19 should be of sufficientthinness in cross-section consistent with its necessary rigidity so asnot to materially obscure the light emitted from any controlled glowingarea or cell of the cathode strip 15. If desired, the line wire anode 19can take the form of a line wire mesh strip, the plane of which extendssubstantially parallel to the cathode 15. Another anode element in theform of a ne wire 20 passes through the mica 13 and has its forward tip21 bent downwardly so as to be in close proximity to the cathode strip15 between the first pair of barrier members 18.

Suitably sealed in a vacuum tight manner through the header of the bulb10 are lead-in wires or contact prongs 22, 23, 24 connected,respectively, to thecathode strip 15, the main anode 19 and theauxiliary anode 21. When the above-described mount has been assembledwithin the bulb 11i the latter can be exhausted in the conventional wayto the exhaust tubulation 25 and lled with a rare gas to the appropriatepressure. The pressure of the rarel gas determines to some extent thesensitivity of the device. By sensitivity here is meant the incrementalcurrent required per complete step or cell of illumination. Thispressure can be as low as two millimeters of neon, with as little as 20microamperes per square millimeter of cathode surface, up to pressuresas high as 40 millimeters and approximately 100 microamperes per squaremillimeter of cathode surface to be illuminated. In either case theimportant feature achieved is that this incremental current is the samefor every cell in the strip. By the term cell is meant the cathode areabetween 2 successive barrier members 18.

The function of the auxiliary anode 21 is to maintain a cathode glow atall times for a given minimum level of signal voltage with which thedevice is to be used. With this minimum signal level only the celldefined by the rst two barrier members 1S and the correspondingrectangular area of cathode 15 with which the auxiliary anode 24cooperates, is illuminated. The remaining cells under this minimum inputsignal condition remain unilluminated. As the input signal level isincreased, one or more of the succeeding cells become cathodeluminescent, the luminescence spreading evenly over the cathode surfaceof each cell and having a well-defined boundary determined precisely bythe width of the cathode 1S and the spacing between adjacent barriers18.

While I do not wish to be conned to any theory as to why the cathodeglow in each cell is confined to the sharply defined boundary of eachcell and does not extend beyond any given cell for a given input signalvoltage, it is possible that the barrier bars 18 accumulate a negativeelectrostatic charge as a result of the ionizing of the gas as long asthe cell area of each cathode between adjacent barrier bars issustaining a cathode glow and the number of successive cells that areilluminated will vary with the level of the input voltage applied toanode 19. Thus, as illustrated in Fig. 5, the electrostatic charge oneach barrier bar may result in a building up of a barrier field aboveeach such bar as represented by the dotted line 26, thus effectivelypreventing the extension of an ionizing discharge between the anode wire19 and the next successive cell. I have found, however, that when theinput signal voltage is increased beyond a certain critical value, thebarrier 26 apparently is insuflicient to prevent spreading of thecathode discharge to the next adjacent cell. In fact it has been foundthat by correlating the input signal level with the number of cells, itis possible to extend the cathode glow in precisely dimensionalincremental spaces along the cathode 15. For example, for the minimuminput signal level, the number l cell only is illuminated, for the nextvalue of input signal level cells numbers l and 2 only are illuminated,and so on, so that for the maximum value of input signal level theentire group of cells, numbers l-l are illuminated.

Referring to Fig. 4 there is shown a typical electrical circuit in whichthe device of Figs. 1 3 may be used. In Fig. 4 the numeral 27 representsa source of direct current voltage, the negative terminal of which isconnected to the cathode strip and the positive terminal of which isconnected through an adjustable signal-controlled resistor 28 to theanode 19. The positive terminal of the source 27 is also connectedthrough a fixed resistor 29 to the auxiliary anode 21. It will beunderstood, of course, that the source 27 and the signal-controlledresistor 2S are merely typical of a suitable source of variable inputsignal level voltage. This source may be either a battery, a powersupply, or any other direct current pulse type input signal supply. Thepotential of source 27 in one arrangement that was found to produce thedesired results had a potential of approximately 250 volts, theresistance 29 was of relatively high value, for example one or twomegohms, which established a sufcient potential on the auxiliary anode21 to keep the number 1 cell luminous by cathode glow. This cell, aspointed out above, is maintained in glowing -condition at all operatingtimes regardless of any other input condition. This illumination of cellnumber l furnishes the ionization which makes the next successive cell,cell number 2, more sensitive to ignition for the next increment ofsignal voltage applied to anode 19, as compared with the sensitivity ofsucceeding cells numbers 3 through l5.

It should be observed that in the absence of auxiliary anode 21 and themaintenance of the cathode glow in cell number l, as above mentioned, apotential applied between cathode 15 and anode 19 would cause a glow tostart somewhere on cathode 15, but the location of this glow would beabsolutely unpredictable. However, by maintaining the number l cellluminous at all times by a suitable minimum voltage applied throughresistor 29 or otherwise, any further increment of potential between thecathode 15 will cause the glow to extend to the next succeeding cell. Inother words, once the glow is established in cell number l, as abovedescribed, the glow will be extended to the next adjacent cell and so onto succeeding cells in accordance with the successive levels of theinput signal voltage applied to anode 19. In other words, theillumination of cell number l predisposes the number 2 cell tosensitivity of glow resulting probably from the spilling over of ionsfrom the number 1 cell to number 2, but of insuicient velocity to causethe number 2 cell to become luminous until the next level of incrementalvoltage is applied to anode 19. Likewise, when cell number 2 becomesluminous it predisposes the next cell, number 3, so that cell number 3becomes luminous only when the next incremental level of voltage isapplied to anode 19.

The resistor 28 may be of any variable kind which changes its resistancevalue with the input signal function to be measured or portrayed on thesuccessive cells. For example, resistor 2S can be a mechanicallycontrolled rheostat, a heat-sensitive resistor or thermistor, a variablevoltage or current supply, and in the event that the power supply 2'7 isof the pulsating kind, the resistor 2S may take the form of a capacitiveor inductive reactance. Whatever form the control device 2d assumes, itmust have minimum and maximum effective values so that the presentedglowing bar along the cathode 15 will be minimum at one extreme of thesetting of device 28, and at the opposite extreme of the setting of saiddevice 28, the glow will be extended to the last cell of the device.

By utilizing various gas pressures and mixtures of gases, a wide varietyof sensitivity can be obtained in the incremental extension of the glowin step fashion to successive cells, with the result that for a giventotal number of luminous cells any length of luminous column can beobtained, for either quite small or quite large changes in the effectivevalue of the resistance 28.

If desired, the movable adjustable element 36 of rheostat 28 can beprovided with a graduated scale 31 having graduated markingscorresponding to the number of luminous cells'within the indicator tube10. Thus in the particular setting shown in Fig. 4, the arm 30 is shownin position number 6, wherein the resistance 28 is adjusted so that thevoltage applied between the cathode 15 and the `anode 19 is such as tocause cells numbers 1-6 to be illuminated. If the member 3() is moved toposition number 5, for example, only cells numbered 1 to 5 areiluminated. On the other hand, if the member 31) is moved to a higherposition7 for example position number 7, the rst seven cells areilluminated so that by this means the column of light in the indicatortube is increased or decreased in precise uniform steps, counting fromcell number l toward cell number l5 in accordance with the setting ofmember 30.

While the drawing shows the device in the form of a straight cylindricaltube 10 and with the mount 11 likewise linear in extent, it will beunderstood that the tube 10 can be bent in any desired shape, such forexample as semi-circular, as shown in Fig. 6, and the mount 11 likewiseis formed with a semicircular configuration. Any other desiredconfiguration of the bulb and mount can be employed.

From the foregoing it will be seen that the device is capable of wideapplication in the measuring and indicating arts. For example, if themember 28 is a thermistor of any well-known kind, the device can be usedas a thermometer, the number of successive cells that are illuminatedindicating the temperature to be measured. Likewise the device may beused 'as a speedometer, in which the resistor 28 instead of beingmanually operated, can be operated by any speed responsive mechanismsuch as the flying ball of any well known governor which is coupled tothe member 30. Likewise the device may be used as a liquid levelindicator, in which case the element 28 can take the form of the movingcore of a reactance. the core being raised and lowered in accordancewith the level of the liquid. In the event that the device is to be usedas a voltmeter, the rheostat 28 may be of fixed resistance value and thevoltage to be measured can be applied between the terminals 32 and 33,as shown in Fig. 7.

Various changes and modifications may be made in the disclosedembodiments without departing from the spirit and scope of theinvention.

What is claimed is:

l. A cathodic glow discharge indicator tube comprising an enclosingenvelope containing a filling of an ionizable medium, an electrode mountwithin said envelope and including a cathode, a corresponding anodeextending along and in spaced relation to said cathode, and a series ofspaced insulator discharge barrier members each extending across thecathode and located between the cathode and anode to form therewith aseries of discrete cells to confine the cathodic glow to one or morecells in accordance with the respective levels of signal control voltageapplied across said cathode and anode.

2. A cathodic glow discharge indicator tube comprising an enclosingglass bulb containing a filling of an inert gas, an electrode mountwithin said bulb comprising an elongated flat cathode, an elongatedanode mounted in spaced relation to and extending along the length ofsaid cathode, a series of insulating barrier members arranged in spacedrelation along said cathode to define therewith 'a series of discretecathodic glow cells, and an auxiliary anode mounted in spaced relationto the cathode in a particular one of said cells.

3. A cathodic flow discharge indicator tube according to claim 2, inwhich said auxiliary anode s in the form of a fine wire having a tipwhich is located in spaced relation to the cathode surface in one ofsaid cells.

4. A cathodic glow discharge indicator tube according to claim 2, inwhich said auxiliary anode is mounted in spaced relation to the firstone of said cells located at one end of said cathode.

5. A cathodic glow discharge indicator tube according to claim 2, inwhich said anode is in the form of a single fine Wire extending parallelto said cathode, and spaced therefrom by said barrier members.

6. A cathodic glow discharge indicator tube according to claim 2, inwhich said anode is in the form of a fine wire mesh extending parallelto said cathode and spaced therefrom by said barrier members.

7. A cathodic glow discharge indicator device for producing a cathodicglow Whose length is accurately controlled in incremental steps bycorresponding applied signal voltages, comprising an enclosing envelopecontaining an ionizable medium, an electrode mount within said envelope,said mount comprising an elongated narrow metal strip cathode, anelongated tine wire anode, insulator members at opposite ends of saidcathode for supporting said cathode and anode in spaced parallelism, aseries of spaced insulator barrier members between the cathode andanode, each extending across the width of the cathode strip and inContact therewith to define a corresponding series of discrete cathodeglow discharge cells, and an auxiliary anode located adjacent only oneof said cells to maintain said one of said cells with a cathodic glowand thereby to form a priming source for the step by step spread of thecathodic glow in successively controlled steps to the succeeding cells.

8. A cathodic glow discharge indicator device according to claim 7, inwhich said insulating members at the opposite ends of the mount areinterlocked with a corresponding pair of insulator strips extendingalong the mount, said barrier members being anchored to and extendingbetween the last-mentioned insulator strips.

9. A cathodic glow discharge indicator device according to claim 7, inwhich said cathode strip is attached to one surface of a flat insulatorstrip which is interlocked with said pair of insulators at the ends ofthe mount.

l0. A cathodic glow discharge indicator device according to claim 7, inwhich said auxiliary anode is in the form of a ine wire having a tipportion which is mounted in spaced relation to the cathode surface ofthe rst one of said cells.

11. Visual indicating apparatus of the cathodic glow kind, comprising agaseous discharge tube having a glass enclosing envelope containing alling of an ionizable medium, an elongated cathode, an elongated anode,means supporting said cathode and anode in spaced relation throughouttheir lengths, and means to cause said cathode to be illuminated bycathodic glow in discrete well-defined successive areas, thelast-mentioned means including a series of spaced insulating barriermembers located in spaced relation along and in contact with the surfaceof said cathode to define a series of discrete cathodic glow cells.

12. Visual indicating apparatus according to claim 11, in which anauxiliary anode is mounted in spaced relation to the cathode in one ofsaid cells, means for applying a steady potential between said auxiliaryanode and said cathode to maintain said one of said cells illuminated bycathodic glow, and means to apply a signal control voltage between saidelongated anode and said cathode to cause successive cells to beilluminated by cathodic glow in step by step succession in accordancewith the successive increments in level of said signal voltages.

No references cited.

